Air leakage detector using a direct pressure system

ABSTRACT

An apparatus for the detection of both small and large leaks in articles. A test article and a reference article are each placed in separate receptacles, subject to a fluid pressure and the receptacles isolated from each other. Should a small leak be present a difference in pressure will appear between the two receptacles. For detecting large leaks, an additional receptacle is placed in communication with each of the receptacles and the pressure difference is checked.

United States Patent [191 Fukuda Feb. 19, 1974 [54] AIR LEAKAGE DETECTORUSING A 3,028,750 4/1962 Rondeau 73 40 DIREUI PRESSURE SYSTEM 3,504,5284/1970 Weinberg 73/493 3,355,932 12/1967 Mulligan 73/493 Akira Fukuda,2-22-8 Kasuga-cho, Nerima-ku, Tokyo, Japan Filed: May 5, 1972 Appl. No.:250,751

Inventor:

Foreign Application Priority Data Aug. 7, 1971 Japan 46 59834 U.S. Cl.73/493 Int. Cl. G0lm 3/02 Field of Search 73/40, 41, 45, 45.1, 45.2,

References Cited UNITED STATES PATENTS 2/1960 Westerheim 73/40 PrimaryExaminer-S. Clement Swisher [57] ABSTRACT An apparatus for the detectionof both small and large leaks in articles. A test article and areference article are each placed in separate receptacles, subject to afluid pressure and the receptacles isolated from each other. Should asmall leak be present a difference in pressure will appear between thetwo receptacles. For detecting large leaks, an additional receptacle isplaced in communication with each of the receptacles and the pressuredifference is checked.

1 Claim, 1 Drawing Figure AIR LEAKAGE DETECTOR USING A DIRECT PRESSURESYSTEM The single FIGURE of drawing is a schematic representation of theinvention.

The present invention may be described by an example, such as the onegiven in the accompanying drawings. The key for the drawing is asfollows: 1: source of compressed air; 2: decompression valve; SVI;threeway electromagnetic valve; SV2, 8V3, V4, SVS: twowayelectromagnetic valves; Cl: air-tight receptacle intended to hold thetest piece (3) which is to be tested for leakage; C2: Airtightreceptacle intended to hold the reference piece (CI and C2 have the samedimensions); Tr: the transducer for detecting the difference in airpressure; TI and T2: air-tight receptacles with smaller dimensions thanCI and C2.

The following procedure is applied with regard to both flow conduits.The decompression valveis used to reduce the air pressure resulting fromthe supply of compressed air. The electromagnetic valves SVI, SV2, and5V3 are opened, and, keeping the electromagnetic valves 8V4 and SVSclosed, air is introduced into receptacles C1 and C2. After a while,valves 2 and 3 are closed. Assuming 30CC for remaining volume ofreceptacles which contained the test piece (3) and the reference piece(4), and 2 cc for the test piece (3), these are then subjected to an airflow at a pressure of 5 kg/cm G. If there is no leakage, the quantity ofair should be 5 kg/cm G X 30 cc; if there is a leak, the vol ume shouldbe 5 kg/cm G X (30+2) cc. When only a small leak is involved, the resultis, as explained above, a difference of pressure between the tworeceptacles, Cl which contains the test piece 3, and C2 which containsthe reference piece 4. The leak may be measured by means of a transducer(Tr), except, however, in the case of a major leak, which rendersmeasurement impossible for the reason that the entry of the compressedair into the two receptacles for an extended period results in thepressure inside Cl and C2 being the same. The aim of the pressureinvention is to be able to detect precisely the force of leaks, even inthe case of major ones. The same procedure, of introducing compressedair into the two receptacles Cl and C2, is used for a major leak. Whenthe current is cut, the electromagnetic valves open, allowing air topenetrate the inner parts of the apparatus, Cl and C2 as well as Tl andT2, which are at atmospheric pressure.

One first opens valves 5V4 and SVS, and with valve SVI closed,compressed air is introduced into receptacles Cl and C2. After a periodof time, the electromagnetic valves SV2 and 8V3 are closed. When thereis no leak in the test piece, the quantity of air will be 5 kglcm GX 30cc. In the case of a leak, this quantity will instead be 5 kg/cm G X(30+2) cc. If the receptacles CI and C2 are considered alone, they willboth have the same air pressure; if, however, valves SV4 and SV5 areopened, the pressure will be changed as it passes to containers TI andT2.

For example, in the case of no leakage, the volume of the receptacle, 30cc, and the volume of the container, 2 cc, give a total volume of 32 cc,providing the following formula:

5 kg/cm G X 30 cc =x kg/cm G X 32 cc The resulting formula fordetermining x is:

in 30/32 X 5=0.9375 X 5=4-.6875 kg/cm G In the case of leakage:

Volume of the air-tight receptacle volume of the test piece leak volumeof the container 34 cc. Or:

5 kg/cm G X 32 cc =x kg/cm G X 34 cc The value of x is therefore:

x= 32/24 X 5 0.94117 X 5 4.70585 kg/cm" G The difference in pressurebetween the two is 4.70585 4.6875 0.01835 kg/cm G. The pressure ishigher on the side where the leak occurs, thus making it possible todetect the leak.

As the volume of the container is small, the pressure on the insidediffers only negligibly from that of the pressure externally supplied.However, an increased volume container will result in a lowering of theinterior pressure of the containers proportionate to the pressuresupply.

As suggested above, the leakage detector of the present invention canuse containers of smaller dimensions than the traditional compressed aircontainers placed in front of the air-tight receptacles. It is for thisreason that this apparatus may be described as simple in structure andeasy to construct. Not only is it smaller, but it performs in a muchmore efficient. and effective manner than traditional devices. We haveseen that it is possible to measure smaller leaks quite: easily eitherbefore or after measurement of major leaks.

I claim:

1. A leakage detector comprising a source of air pres sure other thanatmospheric, a pressure regulating valve and a first cut-off valveconnected in series to the air source; a conduit including two parallelbranches connected to the first cut-off valve; each conduit branchincluding a second cut-off valve, an air tight receptacle, a thirdcut-off valve and a container sequentially connected therein; and adifferential pressure thansducer for indicating the difference inpressure between the two receptacles; the two receptacles being of thesame size and adapted to contain a test or reference piece and the twocontainers being the same size.

1. A leakage detector comprising a source of air pressure other thanatmospheric, a pressure regulating valve and a first cut-off valveconnected in series to the air source; a conduit including two parallelbranches connected to the first cut-off valve; each conduit branchincluding a second cut-off valve, an air tight receptacle, a thirdcut-off valve and a container sequentially connected therein; and adifferential pressure thansducer for indicating the difference inpressure between the two receptacles; the two receptacles being of thesame size and adapted to contain a test or reference piece and the twocontainers being the same size.